The present invention relates to a system for handling foundry sand cores and more specifically relates to such systems which include tooling for forming cavities or receptacles in sand cores, and lifting devices including inflatable arbors for being inserted in and expanded against the wall of the cavity previously formed in the sand core.
In order to improve the finish on casting surfaces, foundry sand cores are often coated or washed with a refractory slurry which is then dried onto the core surface. One way of applying the wash to the core is by dipping the core in a vat containing the slurry. Movement of these cores to and from the vat and into position for entering a drying oven is often accomplished by lifting devices or hoists having at least one arbor insertable into a hole formed in the sand core by a tapered pin located in the corebox when the loose core material is being blown into the corebox. The arbor is of a type including an expandable urethane cylinder which is selectively inflated to swell out against the walls of the hole. Thus, friction is the means for retaining the core on the arbor. Pull tests have shown this method of retention to be variable in effectiveness. For example, the capacity for holding the core on the arbor is diminished when the surface of the wall of the hole is wet, as is often the case when a core wash has been applied to the surface of the core.
U.S. Pat. No. 4,915,157 granted to Durchenwald on Apr. 10, 1990 discloses a core handling device equipped with one or more arbors constructed with an expandable urethane cylinder, as described.